“There is no evidence that any of the vials labeled variola has been breached, and onsite biosafety personnel have not identified any infectious exposure risk to lab workers or the public,” the NIH said.

The vials are now at the CDC’s “high-containment facility” in Atlanta, which is one of only two locations in the world authorized under international law to keep smallpox samples. The second location is the State Research Centre of Virology and Biotechnology (VECTOR) in Novosibirsk, Russia.

The World Health Organization (WHO) was notified and invited to participate in the investigation. Before being destroyed, the samples will be tested over a period of two weeks to see if they are viable. If they are, WHO will be present to witness their destruction.

The virus was officially eradicated 44 years ago following a global public health campaign. At that time, “every single research lab in the world was asked to scour their facilities and submit all specimens for accounting and destruction,” Dr. William Schaffner, an infectious disease specialist at Vanderbilt University, told The New York Times.

It “seems curious beyond belief” that the smallpox vials were now found in an abandoned storeroom, he added.